Turntable on suspended floor - shelf or braces?

I put a Vibraplane isolation platform under my suspended table and it solved all of the problems you mention but also isolates the table so well that I hear all sorts of new detail and extension. The sound improved tremendously. Details can be found on my system page.

My effective inexpensive solution for a suspended turntable (B&O) was to place cryogenically treated tempered steel isolation springs (Machina Dynamica Cryo Baby Promethean Mini-isolators) between the maple board the turntable rests upon and the horizontal top furniture shelf beneath.
For further vibration control, a VibraBlock Damper rests on the horizontal top furniture shelf.
As mentioned by Peterayer above, the sound is upgraded to a surprisingly impressive degree with appropriate isolation.
My turntable is protected down to about 3 Hz which is incredible for the low cost of the setup. When Godzilla next stalks the earth my vinyl won't miss a beat.

Hi djm,

My living room has a suspended wood floor with 20' spans for L and W. A closet, enclosed stairwell and fireplace column on one wall prevent the dreaded "square room" for sonics. But the long span meant bouncy motion even when walking light-footed. I had a heavy cabinet placed by a sidewall but the suspended table still bounced the arm/stylus whenever anyone moved around the room.

I too have a crawl space so I installed three 4x4 posts on concrete footers at 5', 10', and 15' along the center axis of the room. My floor joists run perpendicular to the line of the posts so that helped distribute the support. That cured my floor flex and bouncing stylus problem.

An easier solution might be to mount your turntable support on a load bearing wall. But my floor supports also minimized the floor flex to improve bass response (stiffer boundary) so I gained two benefits.

If you have much flex to your floor it would seem to me any sort of suspension under your table would only be a band aid. Why not cure the ailment instead of taking an aspirin?

Good luck.

djm,

I should have explained that I used an automotive hydraulic jack to raise each of the three floor joists just enough to slip the carefully measured 4x4 posts into place. Then after lowering the jack I didn't even need to nail the 4x4 posts to the joists, but I did drive a couple of framing nails just in case.

Also heavy duty leveling jacks are available for mobile homes, but the three posts and footers were not expensive.

For an easy fix, cram a few paperback books behind the rack or furniture the 'table sits on (as close to the top of the rack as possible) so that the wall will essentially brace the rack and keep it from moving too much as the floor bounces. The more tightly you can wedge the books in there, the better. Fremer mentioned this somewhere on Analog Planet, and it works.